(1) Field of the Invention
The invention relates to data structures and display systems. More specifically, the invention relates to formation and use of a data structure such as a lookup table on a single substrate with a display system.
(2) Background
Liquid crystal displays have been known generally for many years. Initially, liquid crystal displays were formed on amorphous silicon substrates. Amorphous silicon tended to be slow, relatively large, and unsuited for formation of high speed logic and other device types. Liquid crystal displays then evolved into a polysilicon style which still had inadequate speed and logic compatibility characteristics. More recently, crystalline silicon has been employed to manufacture very small liquid crystal on silicon (LCOS) displays. These displays are much faster than the displays which use polysilicon to form display devices and can permit high speed driving of the individual pixels on display. In miniature displays, the challenge is to make the displays as small as possible and to also minimize power consumption, as these displays are increasingly used in a mobile environment with limited power resources.
The use of lookup tables (LUTs) is generally understood in the art. A LUT is effectively a listing of output codes which correspond to the possible input codes. The LUT performs a mapping of the input code to the output code, though the input code and output code may have different ranges. Typically, when LUTs are used in the context of displaying graphical data, three LUTs are employed to carry output codes corresponding to each of the color components (e.g. red, green, and blue) of a pixel. The subsequent three output codes are all simultaneously driven to the display to create the image of the color specified. Using three LUTs per pixel implies non-trivial die space to form the three LUTs, as well as power consumption by all those tables. In the context of miniature displays, it is desirable to minimize both die space and power consumption.
Because driving consecutive positive frames may cause liquid crystal malfunctions, liquid crystal display pixels are invariably driven by an alternating voltage having a positive and negative swing. While this places certain powering constraints on the system, it also necessitates use of frame inversion techniques in which the frame data is inverted to be driven by a negative signal. The required data inversion increases complexity of the display controller as well as power consumption and die are required.
It is also known in the art that liquid crystal displays can be damaged if exposed to DC voltage for a significant period of time. Thus, efforts have been made to reduce the risk of such damage. However, in the case of systems where the display is remote from the display controller, improper cable connections, a crash at the controller, or even a damaged cable can cause large and damaging voltages to be driven to a liquid crystal display. The problem arises how to protect the display from damages as a result of likely faults. Solutions to this problem are largely absent in the existing art.
A method and apparatus employing lookup tables in a time sequential manner is disclosed. A substrate has a display, a digital to analog converter (DAC), and a lookup table (LUT) formed thereon. The LUT is loaded with a LUT data set corresponding to an image subframe to be driven to the display. Successive LUT data sets corresponding to the next subframe are loaded after each subframe is driven to the display. The display in the substrate may be a liquid crystal display or a light emitting diode display or other types of displays. The substrate may be a semiconductor substrate such as a silicon semiconductor having integrated circuits formed therein. The display may be disposed on the same substrate with the LUT or a different substrate, and the DAC may be disposed on the same substrate with the LUT or on a different substrate.
An example of a method of the present invention converts display data from a first set of values to a second set of values through the use of a LUT.
A plurality of lookup table (LUT) data sets are retained in a storage device. The LUT on a display chip is loaded on a first LUT data set of the plurality. Then a first plurality of signals corresponding to a subframe of an image to be displayed are sent to the LUT. A next LUT data set of the plurality may be loaded into the LUT. Once the next LUT data set has been loaded, a second plurality of signals corresponding to a next subframe of an image to be displayed may be sent to the LUT.